/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.function.server;

import java.net.URI;
import java.time.ZonedDateTime;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.function.Consumer;

import org.reactivestreams.Publisher;
import reactor.core.publisher.Mono;

import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.CacheControl;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseCookie;
import org.springframework.http.codec.HttpMessageWriter;
import org.springframework.http.codec.json.Jackson2CodecSupport;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.util.Assert;
import org.springframework.util.MultiValueMap;
import org.springframework.web.reactive.function.BodyInserter;
import org.springframework.web.reactive.function.BodyInserters;
import org.springframework.web.reactive.result.view.ViewResolver;
import org.springframework.web.server.ServerWebExchange;

/**
 * Represents a typed server-side HTTP response, as returned
 * by a {@linkplain HandlerFunction handler function} or
 * {@linkplain HandlerFilterFunction filter function}.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface ServerResponse {

    // Instance methods

    /**
     * Return the status code of this response.
     */
    HttpStatus statusCode();

    /**
     * Return the headers of this response.
     */
    HttpHeaders headers();

    /**
     * Return the cookies of this response.
     */
    MultiValueMap<String, ResponseCookie> cookies();

    /**
     * Write this response to the given web exchange.
     *
     * @param exchange the web exchange to write to
     * @param context  the context to use when writing
     * @return {@code Mono<Void>} to indicate when writing is complete
     */
    Mono<Void> writeTo(ServerWebExchange exchange, Context context);


    // Static builder methods

    /**
     * Create a builder with the status code and headers of the given response.
     *
     * @param other the response to copy the status and headers from
     * @return the created builder
     */
    static BodyBuilder from(ServerResponse other) {
        Assert.notNull(other, "Other ServerResponse must not be null");
        return new DefaultServerResponseBuilder(other);
    }

    /**
     * Create a builder with the given HTTP status.
     *
     * @param status the response status
     * @return the created builder
     */
    static BodyBuilder status(HttpStatus status) {
        Assert.notNull(status, "HttpStatus must not be null");
        return new DefaultServerResponseBuilder(status);
    }

    /**
     * Create a builder with the given HTTP status.
     *
     * @param status the response status
     * @return the created builder
     * @since 5.0.3
     */
    static BodyBuilder status(int status) {
        return new DefaultServerResponseBuilder(status);
    }

    /**
     * Create a builder with the status set to {@linkplain HttpStatus#OK 200 OK}.
     *
     * @return the created builder
     */
    static BodyBuilder ok() {
        return status(HttpStatus.OK);
    }

    /**
     * Create a new builder with a {@linkplain HttpStatus#CREATED 201 Created} status
     * and a location header set to the given URI.
     *
     * @param location the location URI
     * @return the created builder
     */
    static BodyBuilder created(URI location) {
        BodyBuilder builder = status(HttpStatus.CREATED);
        return builder.location(location);
    }

    /**
     * Create a builder with an {@linkplain HttpStatus#ACCEPTED 202 Accepted} status.
     *
     * @return the created builder
     */
    static BodyBuilder accepted() {
        return status(HttpStatus.ACCEPTED);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#NO_CONTENT 204 No Content} status.
     *
     * @return the created builder
     */
    static HeadersBuilder<?> noContent() {
        return status(HttpStatus.NO_CONTENT);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#SEE_OTHER 303 See Other}
     * status and a location header set to the given URI.
     *
     * @param location the location URI
     * @return the created builder
     */
    static BodyBuilder seeOther(URI location) {
        BodyBuilder builder = status(HttpStatus.SEE_OTHER);
        return builder.location(location);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#TEMPORARY_REDIRECT 307 Temporary Redirect}
     * status and a location header set to the given URI.
     *
     * @param location the location URI
     * @return the created builder
     */
    static BodyBuilder temporaryRedirect(URI location) {
        BodyBuilder builder = status(HttpStatus.TEMPORARY_REDIRECT);
        return builder.location(location);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#PERMANENT_REDIRECT 308 Permanent Redirect}
     * status and a location header set to the given URI.
     *
     * @param location the location URI
     * @return the created builder
     */
    static BodyBuilder permanentRedirect(URI location) {
        BodyBuilder builder = status(HttpStatus.PERMANENT_REDIRECT);
        return builder.location(location);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#BAD_REQUEST 400 Bad Request} status.
     *
     * @return the created builder
     */
    static BodyBuilder badRequest() {
        return status(HttpStatus.BAD_REQUEST);
    }

    /**
     * Create a builder with a {@linkplain HttpStatus#NOT_FOUND 404 Not Found} status.
     *
     * @return the created builder
     */
    static HeadersBuilder<?> notFound() {
        return status(HttpStatus.NOT_FOUND);
    }

    /**
     * Create a builder with an
     * {@linkplain HttpStatus#UNPROCESSABLE_ENTITY 422 Unprocessable Entity} status.
     *
     * @return the created builder
     */
    static BodyBuilder unprocessableEntity() {
        return status(HttpStatus.UNPROCESSABLE_ENTITY);
    }


    /**
     * Defines a builder that adds headers to the response.
     *
     * @param <B> the builder subclass
     */
    interface HeadersBuilder<B extends HeadersBuilder<B>> {

        /**
         * Add the given header value(s) under the given name.
         *
         * @param headerName   the header name
         * @param headerValues the header value(s)
         * @return this builder
         * @see HttpHeaders#add(String, String)
         */
        B header(String headerName, String... headerValues);

        /**
         * Manipulate this response's headers with the given consumer. The
         * headers provided to the consumer are "live", so that the consumer can be used to
         * {@linkplain HttpHeaders#set(String, String) overwrite} existing header values,
         * {@linkplain HttpHeaders#remove(Object) remove} values, or use any of the other
         * {@link HttpHeaders} methods.
         *
         * @param headersConsumer a function that consumes the {@code HttpHeaders}
         * @return this builder
         */
        B headers(Consumer<HttpHeaders> headersConsumer);

        /**
         * Add the given cookie to the response.
         *
         * @param cookie the cookie to add
         * @return this builder
         */
        B cookie(ResponseCookie cookie);

        /**
         * Manipulate this response's cookies with the given consumer. The
         * cookies provided to the consumer are "live", so that the consumer can be used to
         * {@linkplain MultiValueMap#set(Object, Object) overwrite} existing cookies,
         * {@linkplain MultiValueMap#remove(Object) remove} cookies, or use any of the other
         * {@link MultiValueMap} methods.
         *
         * @param cookiesConsumer a function that consumes the cookies
         * @return this builder
         */
        B cookies(Consumer<MultiValueMap<String, ResponseCookie>> cookiesConsumer);

        /**
         * Set the set of allowed {@link HttpMethod HTTP methods}, as specified
         * by the {@code Allow} header.
         *
         * @param allowedMethods the allowed methods
         * @return this builder
         * @see HttpHeaders#setAllow(Set)
         */
        B allow(HttpMethod... allowedMethods);

        /**
         * Set the set of allowed {@link HttpMethod HTTP methods}, as specified
         * by the {@code Allow} header.
         *
         * @param allowedMethods the allowed methods
         * @return this builder
         * @see HttpHeaders#setAllow(Set)
         */
        B allow(Set<HttpMethod> allowedMethods);

        /**
         * Set the entity tag of the body, as specified by the {@code ETag} header.
         *
         * @param eTag the new entity tag
         * @return this builder
         * @see HttpHeaders#setETag(String)
         */
        B eTag(String eTag);

        /**
         * Set the time the resource was last changed, as specified by the
         * {@code Last-Modified} header.
         *
         * @param lastModified the last modified date
         * @return this builder
         * @see HttpHeaders#setLastModified(long)
         */
        B lastModified(ZonedDateTime lastModified);

        /**
         * Set the location of a resource, as specified by the {@code Location} header.
         *
         * @param location the location
         * @return this builder
         * @see HttpHeaders#setLocation(URI)
         */
        B location(URI location);

        /**
         * Set the caching directives for the resource, as specified by the HTTP 1.1
         * {@code Cache-Control} header.
         * <p>A {@code CacheControl} instance can be built like
         * {@code CacheControl.maxAge(3600).cachePublic().noTransform()}.
         *
         * @param cacheControl a builder for cache-related HTTP response headers
         * @return this builder
         * @see <a href="https://tools.ietf.org/html/rfc7234#section-5.2">RFC-7234 Section 5.2</a>
         */
        B cacheControl(CacheControl cacheControl);

        /**
         * Configure one or more request header names (e.g. "Accept-Language") to
         * add to the "Vary" response header to inform clients that the response is
         * subject to content negotiation and variances based on the value of the
         * given request headers. The configured request header names are added only
         * if not already present in the response "Vary" header.
         *
         * @param requestHeaders request header names
         * @return this builder
         */
        B varyBy(String... requestHeaders);

        /**
         * Build the response entity with no body.
         *
         * @return the built response
         */
        Mono<ServerResponse> build();

        /**
         * Build the response entity with no body.
         * The response will be committed when the given {@code voidPublisher} completes.
         *
         * @param voidPublisher publisher publisher to indicate when the response should be committed
         * @return the built response
         */
        Mono<ServerResponse> build(Publisher<Void> voidPublisher);

        /**
         * Build the response entity with a custom writer function.
         *
         * @param writeFunction the function used to write to the {@link ServerWebExchange}
         * @return the built response
         */
        Mono<ServerResponse> build(BiFunction<ServerWebExchange, Context, Mono<Void>> writeFunction);
    }


    /**
     * Defines a builder that adds a body to the response.
     */
    interface BodyBuilder extends HeadersBuilder<BodyBuilder> {

        /**
         * Set the length of the body in bytes, as specified by the
         * {@code Content-Length} header.
         *
         * @param contentLength the content length
         * @return this builder
         * @see HttpHeaders#setContentLength(long)
         */
        BodyBuilder contentLength(long contentLength);

        /**
         * Set the {@linkplain MediaType media type} of the body, as specified by the
         * {@code Content-Type} header.
         *
         * @param contentType the content type
         * @return this builder
         * @see HttpHeaders#setContentType(MediaType)
         */
        BodyBuilder contentType(MediaType contentType);

        /**
         * Add a serialization hint like {@link Jackson2CodecSupport#JSON_VIEW_HINT}
         * to customize how the body will be serialized.
         *
         * @param key   the hint key
         * @param value the hint value
         */
        BodyBuilder hint(String key, Object value);

        /**
         * Set the body of the response to the given asynchronous {@code Publisher} and return it.
         * This convenience method combines {@link #body(BodyInserter)} and
         * {@link BodyInserters#fromPublisher(Publisher, Class)}.
         *
         * @param publisher    the {@code Publisher} to write to the response
         * @param elementClass the class of elements contained in the publisher
         * @param <T>          the type of the elements contained in the publisher
         * @param <P>          the type of the {@code Publisher}
         * @return the built response
         */
        <T, P extends Publisher<T>> Mono<ServerResponse> body(P publisher, Class<T> elementClass);

        /**
         * Set the body of the response to the given asynchronous {@code Publisher} and return it.
         * This convenience method combines {@link #body(BodyInserter)} and
         * {@link BodyInserters#fromPublisher(Publisher, Class)}.
         *
         * @param publisher     the {@code Publisher} to write to the response
         * @param typeReference a type reference describing the elements contained in the publisher
         * @param <T>           the type of the elements contained in the publisher
         * @param <P>           the type of the {@code Publisher}
         * @return the built response
         */
        <T, P extends Publisher<T>> Mono<ServerResponse> body(P publisher,
                                                              ParameterizedTypeReference<T> typeReference);

        /**
         * Set the body of the response to the given synchronous {@code Object} and return it.
         * This convenience method combines {@link #body(BodyInserter)} and
         * {@link BodyInserters#fromObject(Object)}.
         *
         * @param body the body of the response
         * @return the built response
         * @throws IllegalArgumentException if {@code body} is a {@link Publisher}, for which
         *                                  {@link #body(Publisher, Class)} should be used.
         */
        Mono<ServerResponse> syncBody(Object body);

        /**
         * Set the body of the response to the given {@code BodyInserter} and return it.
         *
         * @param inserter the {@code BodyInserter} that writes to the response
         * @return the built response
         */
        Mono<ServerResponse> body(BodyInserter<?, ? super ServerHttpResponse> inserter);

        /**
         * Render the template with the given {@code name} using the given {@code modelAttributes}.
         * The model attributes are mapped under a
         * {@linkplain org.springframework.core.Conventions#getVariableName generated name}.
         * <p><emphasis>Note: Empty {@link Collection Collections} are not added to
         * the model when using this method because we cannot correctly determine
         * the true convention name.</emphasis>
         *
         * @param name            the name of the template to be rendered
         * @param modelAttributes the modelAttributes used to render the template
         * @return the built response
         */
        Mono<ServerResponse> render(String name, Object... modelAttributes);

        /**
         * Render the template with the given {@code name} using the given {@code model}.
         *
         * @param name  the name of the template to be rendered
         * @param model the model used to render the template
         * @return the built response
         */
        Mono<ServerResponse> render(String name, Map<String, ?> model);
    }


    /**
     * Defines the context used during the {@link #writeTo(ServerWebExchange, Context)}.
     */
    interface Context {

        /**
         * Return the {@link HttpMessageWriter}s to be used for response body conversion.
         *
         * @return the list of message writers
         */
        List<HttpMessageWriter<?>> messageWriters();

        /**
         * Return the  {@link ViewResolver}s to be used for view name resolution.
         *
         * @return the list of view resolvers
         */
        List<ViewResolver> viewResolvers();
    }

}
